Case IH 520615-02 - UCM – UCM: Rear PTO fender switch stuck on

The control module is receiving a continuous, uninterrupted 'ON' (closed circuit) signal from the external PTO switch located on the rear fender. Because this switch is designed as a momentary push-button, a continuous signal means the switch is either physically jammed, internally shorted, or the wiring harness connecting the switch to the module has shorted to a 12V power source.

• MAGNUM AFS Connect
• Puma series (140, 165, 180, 195, 210, 225)
• Magnum series
• Maxxum series
• Farmall series
• MX series (MX80C through MX170)
• T7 series (T7.220, T7.235, T7.250, etc.)
• T6000
• T7000
• TM series

1. 1

   Inspect the rear fender switch for packed dirt, debris, or physical damage that might be physically wedging the button in the depressed position.

2. 2

   Perform a circuit disconnect test: Unplug the electrical connector at the back of the fender switch and turn the key ON. If the fault code changes from 'stuck on' (5043) to 'open circuit' (Code 5034), the wiring is fine and the switch itself is internally shorted/failed.

3. 3

   Perform a multimeter continuity test: With the switch removed, test across the switch terminals. It should show an open circuit normally, and continuity only when the button is actively pressed. Continuous continuity indicates a dead switch.

4. 4

   Check the wiring harness for a short-to-12V: If you unplug the switch and the 'stuck on' code remains active, the switch is not the problem. You have a short-to-12V in the wiring harness between the fender and the UCM.

1. 1

   Safety First

   Park the tractor on a level surface, turn off the engine, remove the key, and disconnect the negative battery terminal to prevent accidental shorts.

2. 2

   Access the Switch

   Locate the faulty PTO switch on the rear fender. Depending on the model, you may need to remove a protective plastic shroud or access panel behind the fender to reach the wiring.

3. 3

   Disconnect

   Unplug the wiring harness connector from the back of the switch.

4. 4

   Removal

   Depress the retaining tabs (or remove the locking nut, depending on the specific switch part number) and push the switch out through the front of the fender panel.

5. 5

   Installation

   Snap the new OEM switch into the fender cutout until it seats firmly.

6. 6

   Reconnect

   Plug the wiring harness back into the switch. Ensure the weather-pack seal is intact to prevent moisture intrusion.

7. 7

   Clear Codes & Calibrate

   Reconnect the battery. Turn the key ON. You may need to clear the stored error codes from the UCM memory (on some Case IH models, this is done via the 'H8' or 'HC' menu on the instrument cluster diagnostic mode).

8. 8

   Test

   Verify that the code does not return and test the PTO engagement from both the cab and the fender to ensure proper operation.